1. Field of the Invention
The present invention relates to a brake assembly for a vehicle such as motorcycle and more particularly to a brake disk having concentric rings interconnected by a number of heat responsive arms that flex to allow the outer ring to expand radially outwardly and inwardly with respect to the center of the disk.
2. Discussion of the Related Art
Solid one piece brake disks are generally used on motorcycles, bicycles, snowmobiles, and other vehicles. However, the disks tend to warp due to temperature variations from the center of the disk to the outer edge of the disk. Floating rotors are currently used to eliminate warpage, but floating rotors are expensive due to the number of parts and assembly costs.
Brake disks, whether rotary or stationary, must be capable of withstanding the heat created by the friction of brake pads rubbing against the brake disk. Since the heat generated by the brake pads is restricted to the outer perimeter, usually known as the "rim" or "rub area" of the disk, the outer perimeter of the disk expands during braking and contracts after braking. On the other hand, the inner section or "hub" of the disk is heated little if any during braking and, accordingly, does not expand or contract significantly. If a large disparity in temperature exists between the inner and outer areas of the disk, the heated rub area of the disk expands and contracts more than the hub, causing the disk to warp. If the caliper is a fixed mount caliper, as opposed to a slide mount caliper, a warping disk pushes on the pads and pistons on one side of the disk with a resultant loss of braking efficiency.
In U.S. Pat. No. 3,621,945, issued Nov. 23, 1971 and entitled "Disc Brakes," carbon friction disks for aircraft brakes are provided with scalloped perimeters for coaction with driving or restraining elements having similar scalloped perimeters. Both sets of scallops have flat contact surfaces disposed at an angle which optimizes the distribution of force on the friction disk and reduces or eliminates the transfer of heat from the outer rim to the inner rim or hub. In U.S. Pat. No. 3,850,267, issued Nov. 26, 1974 and entitled "Heat Collector And Support For Disc Brakes," a heat-collector shoe is arranged in a guide support which permits movement of the heat-collector shoe perpendicularly to the rotating member. The '267 patent states that the heat-collector shoe and the rotating member can be improved by providing the contact surface of the heat-collector shoe with shallow grooves and the circulation of cooling fluid through internal conduits in the collector shoe body. In U.S. Pat. No. 4,077,501, issued Mar. 7, 1978 and entitled "Disc for Disc Brake Unit," slots are provided in the brake segments which allow for radial expansion and contraction, thereby eliminating cracking by thermal expansion and contraction of the disk.
U.S. Pat. No. 3,435,924, issued Mar. 13, 1967 and entitled "Disk-Brake System with Floating Disk," discloses a floating brake disk having arcuate slots formed in the area between the rub area and the hub which are designed to extend the heat transfer path between the rub area and the hub so that heat is dissipated before the hub can distort. The slots are not designed to accommodate radial expansion and contraction of the rub area relative to the hub and, hence, do not prevent disk warpage.
U.S. Pat. No. 3,301,356, issued Feb. 11, 1965 and entitled "Slotted Brake Disc," discloses a brake disk having slots in its rub area which are designed to relieve biaxial stresses in the rub area. No structures are provided between the rub area and the hub to accommodate radial expansion and contraction of the rub area relative to the hub.
In view of the foregoing, it would be desirable to provide a brake disk, particularly of the type stamped from a nonductile material such as stainless steel, which accommodates radial expansion and contraction of the outer portion of the disk so as to reduce the tendency of the disk to warp, crack, or fracture.
It would also be desirable to reduce the tendency of the disk to warp by allowing the outer annular portion to expand when heated during braking and to contact again after braking. Without this flexibility, the disk may warp after it is heated and then cooled.